The invention relates to a cover plate for an airbag module.
A cover plate for an airbag module, such as for a driver's airbag module, generally has a cover part, i.e. the cover plate, and a plurality of interconnected walls which are connected to the cover part. The walls are generally a front and a rear wall and two side walls which connect the front and rear wall to each other. The walls run rectilinearly or slightly curved in cross section.
Existing cover parts and walls, generally have generally the same wall thickness. Since they are manufactured as a single piece, i.e., by injection molding, at the transition points from the cover part to the walls the manufacturing process may cause sink marks to form on the visible surface of the cover part.
The sink marks can be avoided if the ratio of the wall thickness to the thickness of the cover part is 1:3 to at maximum 1:2. In existing airbag plates, thinned portions are provided on the walls at the transition points to the cover part in order to achieve the abovementioned wall thickness ratio. After the manufacturing, the thinned portions, which constitute undercuts, have to be demolded by a mechanism of slides or by forced demolding. Both types of demolding have disadvantages. Forced demolding may result in deformation of the component. Slides are costly and limit the possibility of designing the tearing seam of the cover plate.
The invention is therefore based on the object of avoiding sink marks on the visible surface of the cover part at the transition points to the walls, with the intention being to provide easy demolding of the airbag plate from the production tool.
In a cover plate for an airbag module, such as a driver's airbag module, the cover plate having a cover part and at least one wall which runs perpendicular to the cover part, the wall, as seen in its cross section, runs in different directions in an alternating manner at distances which are short in relation to the length of the wall. The wall runs in a circuitous manner. With such a cross-sectional profile of the wall, it is possible to design said wall to be substantially thinner than a wall of the prior art, with the same stiffness being obtained in comparison to the previous wall. The abovementioned ratio of the wall thickness to the thickness of the cover part can therefore be achieved without undercuts. Therefore, sink marks can be avoided on the surface of the cover part and, no complicated demolding tools are required. Furthermore, material and therefore also weight are saved. In comparison to the walls of the prior art, a greater freedom of design for the tearing seam of the cover plate is also obtained.
Similar advantages as with a circuitous cross section of the wall can also be obtained if the cross section runs in a curved manner, for example sinusoidally.
Openings for latching a generator support to the cover plate are provided at wall sections which bear against those wall regions of the generator support which are provided with fastening elements. The cross section of the wall changes in direction at the edges of the openings.
The thickness of the wall is half to a third of the thickness of the cover part. In order, at this wall thickness, to achieve an increase in the strength of the wall or in order to further reduce the wall thickness, the wall may have reinforcing ribs. The ribs do not require any additional demolding tools. The reinforcing ribs run generally perpendicular from the cover part without being connected to the cover part.